Toothbrushes having a flexibly linked region in their head are known. For example WO 92/17093 discloses a toothbrush in which the head is divided into two or more segments which are flexibly and resiliently linked to each other and/or to the handle of the toothbrush. A particular form of the toothbrush of WO 92/17093 has a head which has grooves in the reverse face of the head from which the bristles extend, these grooves being filled with an elastomeric material to modulate the flexibility. The embodiments disclosed in have their grooves distributed in a generally uniform distribution over the reverse face of the head, or around the longitudinal mid point of the head, so as to enable the whole head to accommodate itself to the curved shape of the teeth. WO 96/02165 discloses toothbrushes with flexible heads similar in construction to those of WO 92/17093, and having a generally concave profile of bristle ends. DE-G 87 05 474.4 discloses a toothbrush in which the tip region of the head is hinged to a base region of the head and an operating button on the handle allows the tip region to fold relative to the base region.
It is an object of this invention to provide a toothbrush in which the flexibility of the head is concentrated in the tip of the head remote from the handle, so as to improve the ability of the toothbrush to clean surfaces of the teeth which face the back of the mouth.
According to this invention a toothbrush comprises a handle with a head, the head having a base end facing the handle and a tip end remote from the base end, the head adjoining the handle at the base end of the head, the head and handle being disposed along a longitudinal toothbrush axis, the head having bristles extending from a bristle face to the head, characterised in that the head comprises a substantially rigid base region adjoining the toothbrush handle and extending from the base end of the head to a link region situated between the base end and the tip end, and a tip region extending from the tip end of the head to the link region, both the base region and tip region being bristle bearing, the tip region being flexibly and resiliently linked at the link region to the base region.
The above-described construction of toothbrush concentrates flexibility of the head at the tip end of the toothbrush, the linking of the tip region and base region is preferably in a manner which enables the tip region to fold or pivot resiliently relative to the base region during toothbrushing. The link provided at the link region between the tip region and the base region allows the tip region to fold or pivot during use about a fold or pivot axis which is in the plane of the bristle face and generally transverse to the longitudinal toothbrush axis such that bristles on the tip region can lean backwards, i.e. so that the free ends of bristles in the tip region swing toward the handle, assisting the bristles to clean surfaces of the teeth which face the back of the mouth. The flexible linking also helps to prevent excessive brushing pressure from being applied during toothbrushing.
Normally the head of the toothbrush will adjoin the handle of the toothbrush via a neck region between the base of the toothbrush head and the part of the handle which is held during use.
The base region is substantially rigid, that is, during the operation of brushing the teeth the base region does not significantly flex beyond the usual limits of flexing of a plastics material toothbrush head.
The link region is preferably in the longitudinal half of the head furthest from the base of the head. Suitably the base region extends for at least 60%, for example at least 75% of the distance between the base end of the head and the tip of the head.
The tip region may also be substantially rigid, so that the tip region does not itself significantly flex apart from its folding or pivoting relative to the base region. The tip region may be of a variety of shapes accommodated to the shape of the tip of the head, e.g. circular, triangular (including ogival), rectangular, elongate, lozenge shape etc.
In its non-stressed condition, i.e. when not being used, the bristle face of the tip region and base region of the toothbrush of this invention may be substantially coplanar, i.e. with a substantially 180xc2x0 angle between them. In a preferred embodiment of the toothbrush of this invention the bristle face of the tip region forms an angle of less than 180xc2x0 with the bristle face of the base region, e.g. 150-179xc2x0, suitably 155-170xc2x0. A suitable angle is one in which the free ends of the bristles on the handle side of the tip portion are in close proximity to, e.g. touching, the free ends of bristles on the tip side of the base region.
The link region between the tip region and the base region in one embodiment of this invention comprises an aperture, space or chasm in the head material between the tip and base regions which is bridged by means of one or more thin links of flexible and resilient plastics material. In this construction the head is effectively in two regions linked by such links. Such links may comprise thin spines, thin strips, or a continuous thin membrane, made of a both flexible and resilient plastics material. These spines, thin strips or membrane may be in the same plane as a substantially planar head, or may slope or may be curved out of planarity. The plastics material may be the same plastics material as the tip and base regions but being flexible by virtue of thinness, e.g. the tip, base and bridge(s) may be integrally moulded.
In another embodiment of this invention the link region between the tip region and the base region may comprise a composite region between the tip region aid base regions, the composite region having structural elements made of both plastics material and an elastomeric material. For example the composite region may comprise an aperture, space or chasm in the head material between the tip and base regions which is bridged by means of a combination of thin spines, strips or a continuous membrane of a both flexible and resilient plastics material, e.g. integral with the head, and also by an elastomeric material in the aperture, space or chasm. These spines, thin strips or membrane may be in the same plane as a substantially planar head, or may slope or may be curved or folded out of planarity. In this construction the head is effectively in two regions linked by such links, and the links are embedded in a covering layer of rubber.
Such a composite region may for example comprise a net, ladder, latticework, cellular or trellis structure of plastics material integral with the material of the head, with interstices containing the elastomeric material. Such a composite region may for example comprise one or more, for example two, strips of a plastics material integral with the material of the head, the strips being thinner than the thickness of the head, and extending between the tip region and base region to bridge an aperture, space or chasm between the tip region and the base region, the aperture, space or chasm also containing an elastomeric material, suitably bonded to the sides of the space and to the strips and suitably substantially filling the aperture, space or chasm, optionally also bulging above the surface of the surrounding plastics material of the head. Relative to the thickness of the toothbrush head the strips in such a construction may be closer to the bristle face than to the back of the head. The plastics material parts in such a composite region may be thick enough to contribute materially to the flexibility and resilience of the link region, or alternatively they may be so thin as to contribute little to the flexibility and resilience of the link region, and may thus serve simply to retain the tip and head regions together before the elastomer is added.
In another embodiment of this invention the link region between the tip region and the base region may comprise an aperture, space or chasm in the head material between the tip and base regions which is bridged solely by means of a complete or partial filling of an elastomeric material. In this construction the head is effectively in two regions with a gap between them containing the elastomer. This elastomeric material is preferably bonded to the tip region and base region on opposite sides of the aperture, space or chasm so as to hold the tip region and base region together.
The above-mentioned apertures or spaces may comprise a slot, chasm or cut out across the width of the head, dividing the base region from the tip region. Such an aperture may be open at the bristle face of the head and/or at the opposite face of the head, and may pass completely through the head. Such apertures, spaces or chasms may be of various shapes, for example widthways slots. These may in plan be substantially straight aligned widthways, curved or angular, e.g. generally xe2x80x9cCxe2x80x9d, xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d shaped. In such a construction the convex bulge of the xe2x80x9cVxe2x80x9d or xe2x80x9cCxe2x80x9d or the apex of the xe2x80x9cVxe2x80x9d may point either toward the handle or toward the tip of the head away from the handle. Alternatively such aperture, space or chasms may be narrow at the edges of the head and widen toward the centre of the head or vice versa.
Suitably for example the aperture, space or chasm may comprise one or more, preferably one, grooves with a depth of part of the thickness of the head such that the remaining plastics material at the bottom of the groove forms a thin link of plastics material. The groove may then be filled wholly or partly with elastomeric material to form a composite region.
Alternatively the aperture, space or chasm may pass, in places at least, completely through the thickness of the head, for example Leaving bridges of head material crossing the aperture, space or chasm between places where the aperture, space or chasm passes completely through the thickness of the head. Such an aperture, space or chasm may be wholly or partly filled with elastomeric material to thereby form a composite region. When the aperture, space or chasm pass completely through the thickness of the head for the whole of their length they may be wholly or partly filled with an elastomeric material.
The aperture, space or chasm may extend widthways to the sides of the toothbrush head, and elastomeric material therein may be extended around the tip region of the head and/or around the base region of the head to form an elastomeric buffer around the toothbrush head to soften any impact of the toothbrush head with the gums of the user, and also to gently massage the gums. Alternatively elastomeric material may be provided around the tip region of the head to form an elastomeric buffer in a known manner e.g. as in FR 442832 and DE 36 28 722.
When the aperture, space or chasm contains an elastomeric material the outer surface of this elastomeric material may have a corrugated surface, which may further help to control the flexibility of the link region.
In one embodiment of the toothbrush of this invention, the head is constructed such that the tip region may fold backwards resiliently relative to the base region, during toothbrushing, about a widthways oriented fold axis that crosses the head in the link region. The fold axis may cross the head in or on the edge of an aperture, space or chasm as described above. In such a constriction, the aperture, space or chasm may be shaped such that the widthways oriented fold axis crosses the head of the toothbrush entirely within the aperture, space or chasm. When the link region is a composite region as described above, the folding may occur by bending of the above described plastic material parts, or bending at the point where such a part meets the edge of the aperture, space or chasm.
Such a construction can cause the entire tip region to fold in the bristle direction away from the plane which lies between the bristle face and the opposite face of the head, so that the tip region in effect folds backwards towards the base region during use in toothbrushing. This folding can facilitate tooth cleaning, for example enabling the toothbrush head to accommodate itself better to the curved shape of the row of the teeth.
In an alternative embodiment of the toothbrush of this invention, the tip region and/or link may be constructed and positioned such that the tip region can pivot resiliently relative to the base region during toothbrushing, about a widthways oriented pivot axis that crosses the tip region intermediate between its tip end and its base end.
Such a construction causes pivoting of the tip region about this axis intermediate along its length, i.e. causes the tip region to have a xe2x80x9csee-sawxe2x80x9d action in which during toothbrushing part of the tip region toward the tip of the head pivots in the bristle direction away from the plane which lies between the bristle face and the opposite face of the head, and the part of the tip region toward the base region of the head pivots in a direction opposite to the bristle direction away from the plane which lies between the bristle face and the opposite face of the head, or vice versa.
In this embodiment such pivoting may for example be achieved in a construction of head in which the tip end of the base region is in the form of two limbs which partly surround a part of the tip region which extends in the base direction between them, with the link between the tip region and the base region. For example the tip end of the base region may be made in the shape of a two pronged fork-like frame, with a part of the tip region between the two prongs of the fork, and a link between the tip region and base region.
In an alternative construction of the head of this embodiment the base end of the tip region may be in the form of two limbs which partly surround a part of the base region which extends in the tip direction between them, with the link between the tip region and the base region. For example the base end of the tip region may be made in the shape of a two pronged fork-like frame, with a part of the base region between the two prongs of the fork, and a link between the tip region and base region.
For example the tip region may be made generally xe2x80x9cCxe2x80x9d, xe2x80x9cUxe2x80x9d or xe2x80x9cVxe2x80x9d shaped with its limbs toward the base region, or xe2x80x9cYxe2x80x9d shaped with the upper limbs of the Y towards the base region. The part of the base region which extends in the tip direction may lie between the said limbs.
In a construction of head in which the tip end of the base region is in the form of two limbs which partly surround a part of the tip region which extends in the base direction between them, with an aperture between the tip region and the base region, thin links of flexible and resilient plastics material as described above may be provided between the said limbs and the respective tip region. In a construction of head in which the base end of the tip region is in the form of two limbs which partly surround a part of the base region which extends in the tip direction between them, with an aperture between the tip region and the base region, such bridges may be provided between the said limbs and the base region. Suitably in such toothbrushes such bridges may be provided at points widthways diametrically opposite each other to define a pivot axis and to encourage pivoting in a plane in which the longitudinal axis lies. Additionally or alternatively such bridges may be provided at other points in the aperture to encourage pivoting about other axes.
The elastomeric material may be an elastomeric material as commonly used in two-component toothbrushes, e.g. that described in EP 0336641, which can be bonded to plastics materials used for toothbrush handle manufacture. Such an elastomeric material can be injected into the toothbrush mould shortly after injection moulding of the plastics material parts of the toothbrush so that the hot plastics material fuses and bonds with the elastomeric material. This is a generally known process.
In the base region the bristles may be disposed in discrete generally circular section tufts in patterns which are generally known in the field of toothbrushes, for example in longitudinal or widthways rows at a generally conventional spacing. If fused in, the bristles may additionally or alternatively be disposed in xe2x80x9cmatsxe2x80x9d of a cross section which may be circular or other than circular.
In the tip region the bristles may be disposed in discrete generally circular section tufts, or if fused in, the bristles may additionally or alternatively be disposed in xe2x80x9cmatsxe2x80x9d of a cross section which may be circular or other than circular. In the tip region it is preferred to dispose the bristle tufts in either (i) a pattern of discrete tufts arranged in a generally circular or polygonal pattern, or (ii) a single tuft of generally rounded cross section perpendicular to the bristle face, or (iii) a tuft of generally xe2x80x9cCxe2x80x9d or xe2x80x9cVxe2x80x9d shaped cross section perpendicular to the bristle face having at least one of the limbs of the xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d aligned generally parallel to the longitudinal toothbrush axis and with the rounded bend of the xe2x80x9cCxe2x80x9d or xe2x80x9cULxe2x80x9d facing the end of the bristle face remote from the handle.
The ends of the bristles remote from the bristle face may be substantially coplanar. Alternatively the ends may undulate about a plane to accommodate the ends of the bristles to the undulating profile of the teeth or to lie in a xe2x80x9cbattlementedxe2x80x9d shape to help clean the interdental spaces. Such undulating surface bristles are known. Additionally or alternately the ends of the bristles remote from the bristle face on the tip region may lie in a different plane to the ends of the bristles remote from the bristle face on the base region of the head. For example the plane of the said ends on the tip region may slope upwards away from the bristle face in the direction away from the handle. This may for example be achieved in the preferred embodiment of the toothbrush of the invention in which the bristle face of the tip region forms an angle of less than 180xc2x0 with the bristle face of the base region.
The handle may be of generally conventional construction, and may for example include a folded flexible region, and grip pads of elastomeric material, as exemplified in EP 0336641. Elastomeric grip pads may alternatively or additionally be located on other parts of the toothbrush handle as convenient.
The toothbrush of the invention may be made by generally conventional injection moulding techniques, for example in which a plastics material xe2x80x9cskeletonxe2x80x9d is first made by injection moulding, then elastomer parts if present, are introduced by a subsequent injection moulding step, in which the elastomer is injected as a hot fluid and bonds to the plastics material. Such techniques, and suitable plastics materials and elastomer materials, are well known. If the link region includes an elastomer material then this may be injected with the same injection step as is used to inject elastomer grip pads, and these various regions of elastomeric material may be connected by moulding channels in a known manner.
In the embodiment of the invention in which the bristle face of the tip region forms an angle of less than 180xc2x0 with the bristle face of the base region, when the link region comprises the above-described composite region between the tip region and base regions, the composite region having structural elements made of both plastics material and an elastomeric material, the toothbrush is preferably made as follows. Firstly the plastics material skeleton is made by injection moulding, with the bristle face substantially flat, then the tip region is folded to the desired angle with the base region, then the elastomer is injected into the link region.
The bristles may also be of generally conventional construction and materials, and may be fastened into the bristle face by generally known techniques. For example small metal clips around the ends of bristles to be fixed into the head, which are then wedged into sockets in the bristle face. Alternatively the bristles may be fused into the head material, again using known techniques.